Singer fashion disk type B.  Top hat cam #8 Blind stitch.  Will work on many Singer models including: 401, 403, 411, 431, 500, 501, 503, 600, 603, 620, 628, 635, 638, 648, 650, 670, 680, 690, 700, 720, 740, 750, 758. And others.  Price includes shipping to lower 48, return for refund if fails on your machine.